Hitherto, compounds of a group that may release a photographically useful group via a redox reaction are known.
For instance, there are the compounds described in JP-A-61-213847 and JP-A-61-278852 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application") and U.S. Pat. No. 4,684,604.
The known compounds are used for various purposes in accordance with the kind of the photographically useful group to be released therefrom, as so mentioned in the patent publications above.
For instance, in the photomechanical printing field, photographic materials capable of giving high quality reproductions that are stable in a variety of processing solutions as well as simplified replenishment systems are desired for the purpose of meeting the wide variety of diversified and complicated print forms that are now common.
Originals that need to be reproduced and to be employed in a line work process are often composed of a variety of forms such as phototypeset letters, handwritten letters, illustrations, and halftone dot image photographs. These originals almost always contain plural images having different concentration of tone and different line widths, in combination. Photomechanical cameras and photographic materials capable of accurately copying the images from such originals to yield photographic material with good reproducibility as well as image-forming methods applicable to such photographic materials are earnestly desired.
For example, current techniques for producing catalogs or large-sized posters either blow-up or reduce dot image photographs. If the application involves enlarged dot images, the dots must be coarsened which ultimately gives blurred photoprints. If the application requires a reduction of the original, fine dots with an enlarged ratio of the line number per inch must be photographed. Accordingly, the image-forming method having a much broader latitude is desired for the purpose of maintaining the reproducibility of halftone dot image gradation.
A common light source for a photomechanical process camera is a halogen or xenon lamp. In order to obtain sufficient sensitivity to these light sources, the photographic material employed is generally ortho-sensitized. However, it has been found that ortho-sensitized photographic materials are greatly influenced by chromatic aberration of lens and therefore the quality of the images formed are frequently worsened by ortho-sensitization. It has also been found that the deterioration of image quality is more noticeable when a xenon light source is used.
An attempt to satisfy the demand for a broad latitude photographic material for photomechanical printing processes is a lith-type silver halide photographic material composed of silver chlorobromide (having a silver chloride content of at least 50% or more). This lith-type material is processed with a hydroquinone-containing developer having an effective concentration of sulfite ion that is extremely low (generally, to 0.1 mol/liter or less) to thereby obtain a line image or halftone dot image having high contrast and high blackened density where image portions and nonimage portions are clearly differentiated from each other. However, lith-type material and methods of using it have various drawbacks. Because the sulfite concentration in the developer employed in the method is very low, development is extremely unstable due to aerial oxidation. Stabilizing development thus requires additional means and additives. In addition, the processing speed is extremely slow, and the working efficiency is poor.
An improved image-forming system is therefore desired which is free from the problems of the lith-development system, one which may be processed with a processing solution that has excellent storage stability, and one that gives photographic images having ultrahard photographic characteristics. Examples of systems capable of forming an ultrahard negative image having a gamma value of more than 10 have been proposed, such as those in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781. In these patents, a surface latent image-type silver halide photographic material containing a particular acylhydrazine compound is processed with a developer which has an excellent storage stability and which contains a sulfite preservative in an amount of 0.15 mol/liter or more, at a pH value of from 11.0 to 12.3. The image-forming system of each of these patents is capable of processing silver iodobromide or silver chloroiodobromide-containing photographic material, although only high silver chloride content silver chlorobromide photographic material can be processed by previously known ultrahard image-forming methods. While these image-forming systems are excellent for forming images with sharp halftone dot image quality, the processes proceed stably at high speed, and the reproducibility of the image formed is good, further improvement in reproducibility is still desired that will satisfactorily deal with a variety of diversified print forms.
Another way of improving the quality of photomechanical process printing images involves imagewise release of a development inhibitor from redox compounds having a carbonyl group, as illustrated in JP-A-61-213847. However, even employing such compounds, the improvement in halftone dot image gradation of the image formed is still insufficient.
A photographic material is therefore needed which, when developed with a stable developer, provides a high contrast dot image whose tone is broadly controllable.
On the other hand, improvement in working efficiency in a plate making process and dot-to-dot work has been attempted by performing the work in a brighter environment. Accordingly, photographic materials for plate making which can be handled in an environment that may be called a bright room and exposure printers for these materials have been developed.
Photographic materials for daylight use referred to herein mean those which can be safely used for a long period of time under a safelight substantially having a wavelength of 400 nm or more without ultraviolet components.
Daylight photographic materials to be used in plate making work and dot-to-dot work are those which are utilized for negative image/positive image conversions or positive image/positive image conversions where an original of a developed film having letter or halftone dot images thereon is contacted with the dot-to-dot working photographic material for contact exposure. In addition, these materials are required to satisfy the following requirements:
(1) In a negative image/positive image conversion, halftone dot images, as well as line images and letter images, can be converted in accordance with the dot area, line width and letter image width.
(2) Tone regulation of the halftone dot images, as well as regulation of the line width of the letter and line images, is possible.
Various photographic materials for daylight dot-to-dot work which might satisfy these requirements are available.
However, in high technological image conversion work for forming superimposed letter images by dot-to-dot work, the conventional methods of conducting daylight dot-to-dot work using a daylight photographic material is inferior to dark dot-to-dot work method of using the conventional dark dot-to-dot work photographic materials. That is, the quality of the superimposed letter images of the former is worse than the images formed by the latter.
The method of forming superimposed letter images by dot-to-dot work will be explained in more detail with reference to FIG. 1.
In FIG. 1, transparent or semitransparent supports (a) and (c) (generally, polyethylene terephthalate film having a thickness of approximately 100 .mu.m is used) are attached to a letter or line image film (line original) (b) and a halftone dot image film (halftone original) (d), respectively, to form a combined original. A dot-to-dot working photographic material (e) is contacted with the halftone original (d) and with the emulsion surface of the material (e) facing the halftone image surface of the original (d). The material is then exposed to light through the combined original by contact exposure.
After exposure, the material is developed to form transparent line image portions in the dot images.
The important point in this method of forming superimposed letter images is that the negative image/positive image conversion is ideally effected in accordance with the dot area and the line width of the halftone original and the line original, respectively. However, as is apparent from FIG. 1, the halftone original (d) is in intimate contact with the emulsion layer of the photographic material (e). On the other hand, the line original (b) is not directly superposed on the material (e), but with the support (c) and the halftone original (d) being interposed therebetween.
Accordingly, if an exposure sufficient for faithful negative/positive conversion of the halftone original is used, the line original would be out-of-focus because of the space created by the support (c) and the halftone original (d), and the line width in the transparent line image portions in the dot images formed is too narrow. This is the reason for the decrease in quality of the transparent line image portion in the dot images formed.
In order to overcome the above-mentioned problems, a system of using hydrazine has been proposed, for example, as illustrated in JP-A-62-80640, JP-A-62-235938, JP-A-62-235939, JP-A-63-104046, JP-A-63-103235, JP-A-63-396031, JP-A-63-314541 and JP-A-64-13545. However, these hydrazine systems are not sufficient to improve the reproducibility of a dot image gradation, the quality of a superimposed letter image and the reproducibility of a line image, and further improvement is desired.
In color photographic materials, redox compounds capable of releasing a development inhibitor for the purpose of improving the sharpness, improving the graininess and improving the color reproducibility are effective. However, the conventional compounds are unsatisfactory for sufficiently improving the photographic properties of photographic materials of these days which have been increasingly diversified and high leveled. Accordingly, further improvement of the compounds is desired.
It is inevitable that the high sensitized color photographic materials which have been developed recently often sacrifice the sharpness and graininess thereof in some degree for the purpose of elevating the sensitivity thereof. Additionally, disc-size photographic films have poor graininess and sharpness as the enlarged magnification in printing is great.
Moreover, black-and-white photographic materials for X-ray exposure are desired to have an improved sharpness.